Collecting blood samples and delivering aliquots of blood to one or several analytical instruments is a common procedure in medicine. Typically, a patient will have a needle placed in a vein, and multiple tubes containing specific reagents will be filled from that needle. Such a system is commonly encountered in doing a physical examination, or otherwise establishing the state of the patient. As an occasional practice, the drawing of ten to 100 milliliters of blood is normally not of concern. However, if done frequently, such volumes have a potential for lowering red cell density in the bloodstream.
A number of tests for specific conditions, which may need to be repeated frequently, begin by pricking a fingertip with a lancet. Blood flows from the site, and is collected in a capillary, or by collecting a droplet into a test tube or the like. Blood from the collected droplet is then placed in an assay system. This method is unlikely to alter patient blood parameters, but it is poorly suited for multiple tests. It can also be more painful than collecting blood from a vein.
In addition, in most medical situations, blood must itself be treated as a potentially infectious agent. Hence, minimization of potential exposure of personnel to blood is an additional goal. However, because staff time is expensive, the procedures must remain simple and fast even as exposure risk is reduced.
In light of these sometimes competing priorities, there is an ongoing need for simplification of sample handling when drawing blood. Similar considerations apply to clinical sampling of other bodily fluids.